SYNELMIS SIMPLEX. 170 



seta, and by the notocirrus which arises on the notopodial elevation ventrocaudad 

 of the seta. The low elevation continues beneath the neurocirrus which projects 

 laterad as a short subcyUndrical, distally slightly rounded, or subtruncate, setig- 

 erous process, from the base of which on the ventral side arises the neurocirrus. 

 The neuropodia becomes gradually reduced and scarcely evident as distinct proc- 

 esses on the dorsal side of these neurocirri in the caudal region. The notocirrus 

 normally arises from a much constricted narrow base, above which it thickens 

 more or less conspicuously and then tapers subconically and conmionly rather 

 abruptly at the tip ; there is usually a distinct, short, slender tip abruptly set off 

 against the much thicker proximal region. The neurocirri are of very nearly 

 the same form and size as the notocirri, rising from a slender base on a slight 

 basal article and then expanding into a body shaped like a lance-head, or, more 

 commonly, with the body much thicker, egg-shaped, or, more strictly, elliptic in 

 outline, with the slender, transparent tip abruptly set off. Below the slender 

 tips, the surface of the cirri is characteristically marked off in hexagonal areas. 

 (Plate 28, fig. 3). 



The notopodial aciculum is straight and tapers uniformly to an acute tip 

 which does not emerge through the surface; it is colorless. The neuropodial 

 aciculum is similar but a little smaller, and extends into the neuropodium to the 

 distal end. In each notopodium there is but a single seta, which is simple; this 

 is very stout, much exceeding the aciculum in thickness, being two or three times 

 as thick at corresponding levels; it is very stout at base, narrowing rapidly to 

 the apical portion, which projects a short distance only above the surface near 

 the base of the notocirrus; at the apex it is narrowly acutely rounded; it is 

 very densely, finely fibrillate in the longitudinal direction. (Plate 28, fig. 4) . The 

 neuropodium bears a fascia of numerous simple setae, the longest of which extend 

 only to or scarcely beyond the tip of the neurocirrus. The setae are very fine. 

 Each has a slender base above which it widens, and is somewhat flattened in one 

 diameter, and then again narrows to an extremely fine, smooth, and usually 

 curved tip; in a line along one side of the broader portion there is a close series 

 of slender teeth, or pectinae, which extends from the slender base to the beginning 

 of the fine tip. (Plate 28, fig. 5). 



The proboscis dissected out in one specimen is short and seems to be wholly 

 unarmed and smooth, excepting for a series of papilliform folds about the open- 

 ing. 



Locality. Paumotu Islands: Rangiroa Island, Mohican Reef. 23 Sep- 

 tember, 1899. Three specimens. 



